Who developed the Gram stain technique?
Louis Pasteur
Robert Koch
Hans Christian Gram
Alexander Fleming
The Correct Answer is C
A. Louis Pasteur: Louis Pasteur is known for his contributions to germ theory, pasteurization, and vaccines, including those for rabies and anthrax. While he advanced microbiology, he did not develop the Gram stain technique.
B. Robert Koch: Robert Koch established the germ theory of disease and developed techniques for isolating and culturing bacteria, including identifying the causative agents of tuberculosis and anthrax. However, he was not responsible for creating the Gram staining method.
C. Hans Christian Gram: Hans Christian Gram, a Danish bacteriologist, developed the Gram stain in 1884. This differential staining technique allows bacteria to be classified as Gram-positive or Gram-negative based on cell wall properties, greatly aiding in bacterial identification and diagnosis of infections.
D. Alexander Fleming: Alexander Fleming discovered penicillin, the first widely used antibiotic, in 1928. While pivotal in microbiology and medicine, he did not contribute to staining techniques such as the Gram stain.
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Related Questions
Correct Answer is A
Explanation
Based on the image provided, the arrow is pointing to the arm of the microscope.
Arm: The arm is the curved or slanted part of the microscope that connects the base to the head (which contains the eyepiece and revolving nosepiece). It serves two main purposes: It holds the upper portion of the microscope (the optical components) securely above the stage. It is the primary part of the microscope designed to be gripped when carrying the instrument.
Shoulder: The shoulder is the upper supporting part of the microscope where the arm meets the head or body tube. It provides structural support for the optical components and helps maintain proper alignment of the microscope parts.
Correct Answer is C
Explanation
A. Lactose: Lactose in Eosin Methylene Blue (EMB) agar serves as a fermentable carbohydrate source. It allows differentiation of bacteria based on their ability to ferment lactose, producing color changes in the colonies, but it does not inhibit Gram-positive bacteria.
B. Agar: Agar is a solidifying agent that provides a stable surface for microbial growth. It is inert and does not selectively inhibit any bacterial group; its role is purely structural.
C. Eosin and methylene blue dyes: The eosin and methylene blue dyes in EMB agar act as selective agents that inhibit the growth of Gram-positive bacteria while allowing Gram-negative bacteria to grow. These dyes also serve as pH indicators, producing color changes in colonies that ferment lactose, which aids in differentiation of coliforms and other Gram-negative bacteria.
D. Sodium chloride: Sodium chloride maintains osmotic balance in the medium but does not selectively inhibit Gram-positive bacteria. Its concentration is not sufficient to act as a selective agent in EMB agar.
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